feat(terraform-module): allow composition with Auto DevOps modules

Example of pipeline using this version: https://gitlab.developers.cam.ac.uk/uis/devops/infra/terraform/gcp-secret-manager/-/pipelines/451380

The stock Terraform-Module template from GitLab defines its own stages which are almost compatible with Auto DevOps but not quite.

Issue #59 (closed) initially proposed re-working terraform-module.yml to be based on the base template but, really, the only thing that needed to be done was to move the fmt job from the validate stage to test.

(Arguably fmt could be replaced by stuff from /auto-devops/terraform-pipeline.yml but that's for another day.)

Instead of copy-pasting the module, simply import the Auto DevOps stages and move the fmt job.

While we're here, and because this is supposed to be "the One Template To Rule Them All" for terraform modules, also add in a default workflow template a la common-pipeline.yml.

Closes #59 (closed)